Irrigation systems used in homes typically comprise a garage-mounted electronic controller that selectively turns a plurality of solenoid actuated valves ON and OFF in accordance with a pre-programmed watering schedule. The valves admit water to subterranean PVC pipes having several spray, rotor-type or drip-type sprinklers attached to the pipes at spaced intervals. The solenoid actuated valves are usually housed together in a plastic valve box buried near the electronic controller.
In some environments, such as golf courses, so called “valve-in-head” sprinklers are preferred. They have a diaphragm valve built into the lower end thereof which is typically actuated by a solenoid mounted in the sprinkler itself that opens and closes a pilot valve. Each valve-in-head sprinkler on a golf course can thus be individually actuated by an electronic controller usually mounted a considerable distance away.
In U.S. Pat. No. 6,491,235 of Scott et al., assigned to Hunter Industries, Inc., there is disclosed a valve-in-head sprinkler that has a top serviceable diaphragm module. The diaphragm valve module can be readily replaced without excavation and removal of the entire sprinkler if the diaphragm valve module is worn, damaged by grit or otherwise defective, e.g. if there is leakage from the top of the outer sprinkler case when the valve is in its OFF state. The telescoping riser that contains the nozzle, turbine and gear drive train is first removed from the outer sprinkler case. The diaphragm valve module, which is mounted in the lower end of the outer sprinkler case, can then be withdrawn and replaced.
Valve-in-head sprinklers typically operate at a relatively high pressures, e.g. over one hundred PSI, and in some cases as high as two hundred PSI. When the valve is in its CLOSED or turbine state such high water pressures place substantial strains on the mechanical components which can lead to failures. It would be desirable to have an improved replaceable valve module for a valve-in-head sprinkler that alleviates this problem.